DE1292199B - Transductor with alternating current output, which has two separate cores - Google Patents

Description

The invention relates to a transductor, which consists of two inductive separated from each other, provided with several windings and self-contained There are cores which can be premagnetized by means of windings through which direct current flows are.

The transductor or also called the magnetic amplifier has been the last Time as a particularly reliable control and regulating element in automation of work processes found a relatively large area of application. The basic element of a transducer is a direct current biased alternating current coil with ferrite cores.

The non-linearity of the magnetization characteristics of iron cores can be exploited to use a transductor as a magnetic amplifier element to use. Each coil with ferrite cores takes a small AC voltage only a small alternating current, which increases very quickly when the coil reaches the area of magnetic saturation. The course of the relationship between induction and magnetic field strength representing the magnetization characteristic between the unsaturated and saturated area of the core depends on the properties the core material used as well as the core shape. One lets through a a control winding additionally attached to the iron core allows a direct current to flow, thus the iron core can be pre-magnetized in a suitable manner and consequently the operating point on the magnetization characteristic can also be determined accordingly. If you close a choke coil, also located on the core, in series with one Consumer, you can see its current consumption by changing the inductance of the Modify the transductor by means of direct current bias.

It is already known to assemble the transducer from two windings and to switch the control windings against each other so as to prevent the same influenced by the induction effect of the alternating voltage of the working winding will. In addition to this so-called electrical decoupling of the control winding also known the magnetic decoupling, in which you have two cores with one common control winding provides, so that the alternating flows of the work windings cancel with respect to the control winding.

The invention is based on the object of an electrical control device in the form of an improved transducer that can be connected upstream to a consumer is, with disadvantages that have arisen up to now due to relatively high initial impedance values in the unexcited state of an inductive load and low impedance values in the excited state of the same avoided or enables such a working characteristic can be. The control device according to the invention should therefore be used for highly inductive Consumers, for example for squirrel cage motors, one required for their start-up strong feedback current peak can be made available, the value of which depends on the the respective size of the adjustment voltage depends on which one is used between Winding groups is available, being after start after the acceleration current peak has subsided, the feedback excitation is to be controlled so that it is automatic decreases with the consumer current. It is known that the starting current is in squirrel cage motors several times over its full load value. The solution to the problem according to the invention is achieved by the fact that the consumer current flows through the two Cores applied main winding arrangement divided into equal half-windings is that on the legs of each core with opposite winding directions are connected in parallel to each other, with the half-windings at the same time on one core to the corresponding half-turns on the other core in Are connected in series, and that between the connecting line of the half-windings with one direction of winding and the connecting line of the half-windings with the reverse winding direction a rectifier is provided.

A further development of the invention is that an additional Control winding arrangement is provided, one pair of half-windings with the associated other two half-windings each in the opposite direction of rotation on the two legs of the cores are divided, with the half-windings lying in series are connected in parallel to each other and between the connecting line of the half-windings with one direction of winding as well as the connecting line of the half-windings with a rectifier is provided for the opposite winding direction.

It is also important for the invention that the direct current actable excitation winding arrangement consisting of two identical, synchronous in each core There is magnetic flux generating half-winding pairs.

Further characteristics and features of the electrical according to the invention Control device with a transducer connected upstream of the consumer go out the following description in conjunction with the drawings.

From the electrical control device according to the invention result the following advantages: When starting the squirrel cage motor, the according to the invention designed transducer a sufficient feedback current available, the size of which depends on the voltage difference between the connecting lines of the two half-winding patterns on the two cores depends, the difference being the instantaneous voltages between the half-windings in the two local circuits by the level of supplementary excitation in the excitation winding arrangements charged with direct current as well as depends on the eigenvalues of the rectifier. When the squirrel cage motor has reached its normal speed, the feedback excitation automatically decreases with the current flowing through the main windings, the impedance level of the Transductor in a relatively large load area of the consumer is kept constant and by the excitation windings or the one sent through them Direct current is preselectable. By means of the control device according to the invention is the maximum value of the feedback without the previously detrimental instability realizable, as in the case of the so-called oversized one used so far Feedback excitation appeared. The impedance of the transducer is im The consumer's state of excitement can be reduced to a significantly lower value, than has been possible with conventional prior art devices. According to the invention possible Decreasing the value of the continuous impedance of the transducer turns out to be very great advantageous, while also keeping the physical dimensions of the device in very small Limits can be kept.

The drawings show, for example, embodiments of the electrical control device according to the invention, and it denotes F i g. 1 shows the schematic representation of a transductor connected upstream of a single-phase squirrel cage motor, FIG. 1 a shows an embodiment of the circuit possibility of an additional control winding, FIG. 2 shows a schematic representation of the flux conditions in the main winding during the positive half-wave of the alternating current, FIG. 3 shows a representation according to FIG. 2 during the negative AC half-wave, F i g. 4 shows a corresponding representation for the control winding during the positive half-wave, FIG. 5 shows a representation according to FIG. 4 during the negative half-wave, F i g. 6 shows the voltage curve falling across the rectifier T 1 or T 2 in relation to the voltage curve of the network, FIG. 7 and 8 a schematic representation of the currents induced within the control windings during the positive and negative half-cycle of the alternating current, FIG. 9 shows an application example of the control device according to the invention for the operation of a three-phase motor, FIG. 10 is a schematic diagram of optional excitation winding arrangements; and FIG. 11 shows a modified circuit arrangement from FIG. 2.

In the drawings of FIG. 1 shows an electrical control device according to the invention with a transducer connected upstream of the consumer M. The consumer M consists of a single-phase alternating current squirrel-cage motor, the current-feeding line being denoted by L 1 and L 2. The transducer consists of two completely identical, self-contained cores A and B made of highly permeable magnetic material, for example a silicon-iron or a nickel-iron alloy. Half of the main windings PA and PB through which the consumer current flows are each applied to a leg A 1 and A 2 of core A and legs B 1 and B 2 of core B. The half-windings Pa 1 and PA 2 or PB 1 and PB 2 are connected in series via the lines 16 and 17, while on the other hand the half-windings PA 1, PB 1 are parallel to the half-windings PB 2, PA 2. The main winding arrangement is connected to the single-phase network L 1 via the line 18, and the line 19, on the other hand, connects the main winding arrangement to the squirrel-cage motor M. The circuit is closed via the line section L 2. Electrically completely decoupled from the main windings, an excitation winding arrangement is also provided on cores A, B , which is composed of half-windings NB 1 and NB 2 on core B and NA 1 and NA 2 on core A. The excitation winding arrangement is connected to a direct current source x, y, the following current curve being displayed: The negative pole y is connected via the line 24 to the half-winding NA 1 , which in turn is connected via the line 20 to the half-winding NA 2 . The line 21 bridges the output of the half-winding NA 2 with the input of the half-winding NB 1, which is connected on the output side via the line 22 to the half-winding NB 2 . Finally, the circuit to the positive pole x of the direct current source is closed via line 23 and a control switch K. A choke N can advantageously be introduced into the direct current circuit.

As long as the control switch K is open within the excitation circuit is, flows through the main winding arrangement PA, PB, a current that the small Magnitude of the magnetizing current of the transducer, the impedance of which is very large, is equivalent to. The voltage drop across the motor M is to be set approximately to zero. By preselecting the winding direction of the half-windings of the main winding arrangement has the instantaneous magnetic flux within the nuclei during the positive Half cycle of the alternating current corresponds to that in the first drawing of FIG. 1 through the Parts p given direction. During this half-period, therefore, flows within the Core A the flow counterclockwise, while in core B it is clockwise running around.

When the control switch K of the excitation winding arrangement NA, NB is closed, an additional flow is created within the self-contained cores, which flows clockwise in both cores. The additional flow is shown schematically in the drawing in the dashed lines e shown with arrows. It can also be seen from the drawing that when a direct voltage is applied to the excitation winding NA, NB, the total magnetic flux within the core A is reduced, while the flux in the core B is increased.

In Fig. 2 these overlapping rivers are again schematically shown, whereby the magnetic fluxes increasing in superposition with H and the rivers that partially cancel or weaken each other are denoted by L. are. The representation in FIG. 2 again refers to a snapshot, during the positive half cycle of the alternating current. The direction of the current within the Main windings are shown by arrows next to the half-windings. The to it analogous conditions during the negative half-wave of the applied alternating current are in Fig. 3 pictured. According to the magnetic flux conditions within the cores as well as the mutual coupling of the half-windings is created between the two Line sections 16 and 17 a constantly changing voltage potential, which is equal to the difference resulting from the high and low instantaneous potentials of the half-windings of the main winding arrangement results. The one between the lines 16 and 17 resulting alternating current, which is the direct result of the relative magnetic imbalance between the two nuclei can occur at the two midpoints W 1, W 2 are tapped. According to the invention, between points W 1 and W is 2 a rectifier T 1 is provided.

By bridging the line points W 1, W 2 by means of the rectifier T 1 , two independent circuits are now created, and the alternating voltage that arises between the two line points can be used for feedback purposes. The two local electrical circuits formed by the rectifier bridging include half the main windings PA 1 and PB 2 and the rectifier T 1 and, on the other hand, the main winding halves PB 1 and PA 2 and again the rectifier T 1. As in FIG. 2, according to the above, during the positive half-wave of the alternating current of the network, a circulating current from the winding half PB 2, over which a high voltage drops, will flow clockwise via the winding half PA 1 and the rectifier T 1. At this moment, the low voltage labeled L drops across the winding half PA 1. At the same time, in the right circuit via the winding half PB 1 with a large voltage drop, a current also flows clockwise through the winding half PA 2 with a low voltage drop also via the rectifier T1 in Fig. 2 is shown with the dashed circular path f. Both circuits are superimposed by the direct current flow within the field winding halves NA, NB , the flow of which is represented by the circular paths e, which are also shown in dashed lines. The excitation magnetization runs in the direction of the clockwise movement in both circles. The flow directions in the schematic representations of FIG. 2 to 7 and in FIG. 8 indicate reversed directions within the two circuits is because these representations consider the two cores A and B lying flat in the plane of the paper, with core A viewed from above from the front, while core B with respect to FIG. 1 is illustrated as being rotated by 180 °, ie viewed from the rear.

In Fig. 3 shows the different, overlapping flows during the negative half-wave of the alternating current. The arrow directions p according to FIG. 1 turn around while maintaining the direction of the supplementary excitation. During the positive half-wave, a harmonically alternating voltage potential arose between points W 1 and W 2 with a frequency of fluctuation that was doubled compared to the supply voltage frequency. With the opposite sign, the conditions during the negative half-wave of the alternating current are completely analogous to this. In Fig. 3, the half-windings over which the high voltage potential drops are again designated by H and those over which the lower potential drops are designated by L. The circulating feedback currents in both local circuits thus flow simultaneously in a clockwise direction through the two main windings, namely during the positive and the negative half-cycle, as illustrated by the circular paths e and f. Because the circulating currents brought in one direction create a feedback excitation in the associated half-windings of the main winding arrangement, the direction of which is the same as that of the supplementary excitation by the excitation winding arrangement NA, NB , a powerful feedback current is available when the squirrel-cage motor in series with the transducer is started, the size of which depends on the inequality of the voltages applied between points W 1, W 2 of the two winding groups PA 1, PB 2 and PB 1, PA 2 . This in turn is determined from the size of the supplementary excitation applied and from the impedance of the half-windings and the rectifier. When the squirrel cage motor M has reached the normal operating state after the start-up peak, its power consumption drops several times over, the feedback excitation automatically decreasing with it.

Although, according to the above, the feedback effect within the Main winding arrangement PA, PB is completely feasible, it is in some cases it is desirable to provide separate feedback windings. From the main winding arrangement separate feedback winding arrangements are required, for example, when high voltage is to be used or also when at low voltages a consumer with a very high current consumption is to be connected. By means of separate Feedback windings, the transducer can be used as a current transformer.

In Fig. 1 shows such feedback windings provided separately from the main winding arrangement in the form of a control winding arrangement SA 1, SA 2, SB 1, SB 2 . The control winding arrangement is applied to the two legs of each core A, B in the same way as the main winding arrangement. The coupling between the main winding arrangement and the control winding arrangement is purely inductive. The half-windings SA 1 and SA 2 are wound on the core A , while the corresponding half-windings SB 1 and SB 2 are located on the core B. The half-windings SA 1, SB 1 show opposite winding directions compared to the half-windings SB 2, SA 2 , whereby they are parallel to one another. A rectifier T 2 is interposed between the connecting line 25 of the half-windings SA 1, SB 1 and the connecting line 26 of the half-windings SB 2 and SA 2. By attaching the rectifier T 2 to the contact points W 3 and W 4, two separate circuits are created here, as with the main winding arrangement, one of which is the half-windings SA 1 and SB 2 and the rectifier T 2 and the other the half-windings SA 2, SB 1 and also include the rectifier T 2. In Fig. 4, the switching arrangement is indeed schematic, but clearer or clearer than in FIG. 1 shown. The direction of flow during the positive half-wave of the alternating current is illustrated by the arrows shown next to the half-windings in this figure. When the excitation voltage acts on the transducer, which creates a magnetic or magnetic imbalance in the core, an induced harmonic alternating current potential of twice the feed frequency is formed between the points W 3 and W 4, as has already been described for the main windings PA, PB is. In the two right and left circuits circulating currents flow simultaneously, namely from the half-winding SB 1 with a high voltage drop during the positive half-cycle in an anti-clockwise direction, through the half-winding SA 2 with a low voltage drop and through the rectifier T 2 on the one hand and through the half-winding SB 2, the rectifier T 2 and the half-winding SA 1 with a low voltage drop on the other hand. The two circulating currents thus flow alternately in the same direction through the windings and thus generate a feedback excitation, the positive and negative superimposition in turn being shown by the dashed circular paths e and f. The analogous conditions in the two local feedback circuits during the negative half cycle of the alternating current are shown in FIG. 5 illustrates. After what has been said above, it is easily possible for the average person skilled in the art to clarify the corresponding relationships during this half-period with the aid of the drawing.

Another possible switching arrangement for the control winding SA, SB is shown in FIG. 1 a shown. Here the connection terminals of lines 25 and 27 of half-winding SA 1 and lines 26 and 28 of half-winding SA 2 are interchanged. In the in F i g. 1, the potential between the points W 3 and W 4 of the control winding arrangement SA, SB is equal to zero in the de-energized state and equal to the maximum in the energized state, while that between the points Z 3 and Z 4 according to FIG. 1 a is equal to the maximum in the unexcited state and zero in the excited state. However, as further from FIGS. 7 and 8 can be seen, the achievable results are shown in the arrangements according to FIG. 1 and 1 a are the same, which can be clearly seen from the direction of the voltage potential applied to the winding halves and from the circulating feedback currents within the local circuits during the positive or negative half-cycle. F i g. 7 shows the voltage or flow conditions during the positive half cycle of the supply voltage during FIG. 8 illustrates the corresponding status information during the negative half cycle. The half-windings with the high voltage component are again labeled H and those with the low voltage drop are labeled L. What has already been said for the main windings applies here accordingly.

In Fig. 6 shows the waveform of the alternating voltage, with 12 meaning the alternating voltage from the supply network, while the alternating voltage denoted by 13 is that which is between the points W 1 and W 2 or W 3 and W 4 or also Z 3 and Z 4 occurs. It can be clearly seen that the alternating voltage drop across the rectifier T 1 or T 2 has twice the frequency of the alternating voltage of the network. The period O 2 of the induced harmonic voltage is half as long as the period Q 1 of the mains voltage. The hatched negative half cycle of the alternating voltage occurring between points W 1 and W 2 is suppressed by the rectifying effect of the rectifier T 1 or T 2.

To F i g. 1 would have to be added that in the drawing of the excitation winding arrangement intended throttle N is provided because specifically in conjunction with a Single-phase circuit the inductive effect of the double-frequency harmonic voltage causes a superposition to the supplementary excitation, the intended choke coil N compensates for the double-frequency voltage component and thus its circulation prevented by the exciter rectifier system during the positive half cycle.

If the direct current source of the excitation winding arrangement NA, NB is to be variable, according to FIG. 1 a potentiometer controller KR can be provided.

While the described transducer mainly for single-phase supply systems can be used, it can also be used for three-phase systems. Therefore are three such units with the engine or the consumer in star or Delta connection connected.

F i g. 9 shows a typical arrangement in which three single-phase units, each according to FIG. 1 arranged, can be used, but with the separate additional Feedback windings or control windings are omitted.

The arrangements C 1-C 2 and C 3 are star-connected between the line L 1 and the terminal 41 of the three-phase squirrel cage motor M, the line L 2 and the motor terminal 42 and the line L 3 and the terminal 43. The motor M is a delta winding machine shown, but it can just as well be star-wound. Likewise, the converters can be designed and connected in delta instead of star, although the latter arrangement is preferable from the point of view that in the de-energized state the converters C 1-C 2 and C 3, the motor terminals 41, 42 and 43 are jointly at zero potential.

The excitation power supply source, as shown in the schematic diagram, is derived from a three-phase rectified power supply comprising a three-phase transformer R, the primary winding Rp of which is connected to the three-phase power supply system at L 1, L 2 and L 3, while the secondary windings Rs and the three-phase full-wave rectifier system T 6 supplies power for the supplementary excitation, namely from the positive terminal via the control switch K, the line 44 through the excitation winding system C 1, connected in parallel, through the line 45 to the excitation winding system C 2, connected in parallel, through line 46, through the excitation winding system on converter C 3, also in series, and back through line 47 to the negative terminal on the excitation rectification system.

In the illustrated. Arrangement are the excitation windings on the Cores in a non-inductive relationship to the main AC magnetization in Connected in series as described in the single-phase examples, with the both groups are connected in parallel. The excitation windings of the units in the various phases are, as is more clearly shown in FIG. 10 is shown with each other grouped in series in an open delta connection. This makes the inductive ones stand out Tensions from the different phases, variable or non-variable in character, which are caused by the inherent imbalance of the alternating current flows, due to the circuit relation of the open triangle itself. This is the Sum of the individual inductive voltages between lines 44 and 47 to all Times zero between which the excitation supply voltage is preferably of one rectified three-phase power source is supplied, as shown in FIG. 9 des is shown in more detail as a DC power source. If a suitable Smooth run Should be provided, however, an excitation caused by rectified Single-phase power sources are used.

Interconnecting the excitation windings of the three transducers the F i g. 9 includes the in F i g. 10 dashed connections with a. The most complete Neutralization of the inductive voltages is achieved, however, when the in F i g. 10 connections shown in dashed lines are omitted.

Where total feedback windings are used, they can either be connected in parallel, resulting in two local circuits, or in series be connected to create a local circuit through the rectifier is completed, or the windings can be mutually disconnected and in each case individually bridged by a separate rectifier.

As for the feedback arrangements described, here is assumed that they give a positive feedback excitation, but where a negative one Feedback is required, as shown in FIG. 11 is shown by means of a separate rectifier T 1 B can be achieved, the positive feedback rectifier is oppositely polarized and which is between the midpoints of the windings W 1, W 2 (or W 3, W 4 or Z 3, Z 4 in the other figures) in series with one suitable resistor Rn is switched on. So it is achieved that the feedback excitation flows through the main windings in a direction which is the complementary excitation is opposite. Such negative feedback can be associated with certain Protection orders may be required.

As already mentioned, those are between the midpoints of the main winding arrangements existing voltage fluctuations from twice the feed frequency, and the In the last example of the negative half-cycles, the feedback rectifier allows by the bias resistor Rn during each half cycle of the normal supply voltage frequency to go through. It is thus clear that positive and negative feedback excitations have a mutual phase shift of 180 °.

The positive feedback excitation is of course given by the amount of the generated negative feedback is reduced, as is normally the case with conventional devices.

But it is done by omitting the negative feedback rectifier TIB and using the resistor Rn only between the midpoints of the winding system a circulating feedback current will flow in the negative direction during the negative half cycles of the double frequency feed. In the positive Direction is lagging with 180 ° on the dual frequency scale, with 90 ° Lag correspond to the basic frequency scale. That flow in the positive direction will be added to the positive feedback, the result of which will be that there is no reduction in the positive feedback through the coexistence of the negative Feedback is generated.

Claims (3)

Claims: 1. Transductor with alternating current output, which consists of two inductively separated cores provided with several windings and closed in themselves, which can be pre-magnetized by means of windings carrying direct current, characterized in that the consumer current carrying the current is applied to the two cores (A, B) applied main winding arrangement (PA, PB) is divided into equal half-windings (PA 1, PB 1 and PA 2, PB 2) , which are placed on the legs (A 1, A 2 and B 1, B2) of each core (A, B) are parallel to each other with opposite winding directions, with the half-windings (PA 1, PA 2) on one core (A) in series with the corresponding half-windings (PB 1, PB 2) on the other core (B) are connected, and that between the connecting line (16) of the half-windings (PB 1, PA 1) with one direction of winding and the connecting line (17) of the half-windings (PB 2, PA 2) with the reverse winding ungssinn a rectifier (T1) is provided. 2. Transductor according to claim 1, characterized in that an additional control winding arrangement is provided, one pair of half-windings (SA 1 or SB 1) with the associated other two half-windings (SA 2 or SB2) each in the opposite direction of rotation on the two legs (A 1, A 2 and B 1, B 2) of the cores (A, B) are divided, the series half-windings (SA 1, SB 1 and SB 2, SA 2) being connected in parallel to each other and between the connecting line (25) of the half-windings (SA 1, SB 1) with one direction of winding and the connecting line (26) of the half-windings (SB 2, SA 2) with the opposite direction of winding, a rectifier (T2) is provided. 3. Transductor according to claim 1, characterized in that the excitation winding arrangement (NA, NB) which can be acted upon by direct current consists of two identical half-winding pairs (NA 1, NA 2, NB 1, NB 2) generating magnetic fluxes in each core (A, B). consists.